WORCESTER — One of the JetBlue flights scheduled to leave Worcester Regional Airport Friday is among 12 that have been canceled because of dreary weather or mechanical problems since the airline began service here just a month ago.

Three Thursday flights — two arrivals and one departure — were scratched because of foggy weather.

On top of the cancellations, four flights scheduled to land in Worcester were diverted to Boston because conditions here made it difficult for planes to land. Daily flights from Worcester to Fort Lauderdale and Orlando, Fla., began Nov. 7.

"This is a slightly higher number of cancellations and diversions compared to other cities we fly to," JetBlue spokesman Bryan Baldwin said. "It's mostly because the airport is easily affected by weather, which can easily put the airport below our operational requirements."

The airline employs meteorologists who monitor weather conditions 24 hours a day. The foggy conditions in Worcester this week are part of a larger weather pattern, Mr. Baldwin noted.

"We're trying to find the right balance of letting our customers know as soon as we can, but being as certain as we can about the forecast," he said. "We want to be proactive and alert our customers so they can make decisions about other flights."

Customers affected by the cancellations were allowed to rebook to JetBlue flights in Worcester or Boston, where JetBlue is the largest carrier. In some cases the airline automatically rebooks disrupted passengers.

John Ambrose of Worcester, returning Thursday afternoon from a family trip to Disney World, was among the Worcester passengers shifted to flights landing in Boston. After collecting their baggage, he and other passengers were bused back to Worcester where they had parked their cars.

"It's frustrating, but overall I am really satisfied with JetBlue," he said. "They're doing everything right to make up for it."

Other more disgruntled passengers vented about the flight disruptions on Twitter.

JetBlue plans to explain the weather issues in Worcester in a blog post this week.

Fog at the hilltop airport has been a longtime problem, prompting the Massachusetts Port Authority to commit $32 million to upgrade the airport's landing systems. The project is expected to take at least five years, much of that time spent in permitting.

JetBlue's service in Worcester began after the airport sat empty, except for general aviation, since early 2012. Airline executives said the enthusiasm they found for JetBlue in Worcester was unparalleled.

Massport spokesman Richard Walsh called the airline's service in Worcester a success — the flights have been about 80 percent full — but didn't comment on the cancellations.

"We're thrilled with the JetBlue service at Worcester airport," he said.

Massport officials want JetBlue to ramp up service in Worcester to bigger planes, more daily flights and destinations beyond Orlando and Fort Lauderdale. The airline, brought to Worcester with the help of $1.2 million in public incentives, is under no obligation to stay in Worcester if the location doesn't meet its profit targets.

The Worcester airport is expected to pump $369 million into the regional economy over the next 10 years, according to a $10,000 study commissioned by Massport.